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       1                 :            : /******************************************************************************
       2                 :            :  * Top contributors (to current version):
       3                 :            :  *   Andrew Reynolds, Aina Niemetz
       4                 :            :  *
       5                 :            :  * This file is part of the cvc5 project.
       6                 :            :  *
       7                 :            :  * Copyright (c) 2009-2024 by the authors listed in the file AUTHORS
       8                 :            :  * in the top-level source directory and their institutional affiliations.
       9                 :            :  * All rights reserved.  See the file COPYING in the top-level source
      10                 :            :  * directory for licensing information.
      11                 :            :  * ****************************************************************************
      12                 :            :  *
      13                 :            :  * dynamic_rewriter
      14                 :            :  */
      15                 :            : 
      16                 :            : #include "cvc5_private.h"
      17                 :            : 
      18                 :            : #ifndef CVC5__THEORY__QUANTIFIERS__DYNAMIC_REWRITER_H
      19                 :            : #define CVC5__THEORY__QUANTIFIERS__DYNAMIC_REWRITER_H
      20                 :            : 
      21                 :            : #include <map>
      22                 :            : 
      23                 :            : #include "context/cdlist.h"
      24                 :            : #include "theory/uf/equality_engine.h"
      25                 :            : 
      26                 :            : namespace cvc5::internal {
      27                 :            : 
      28                 :            : class Env;
      29                 :            : 
      30                 :            : namespace theory {
      31                 :            : namespace quantifiers {
      32                 :            : 
      33                 :            : /** DynamicRewriter
      34                 :            :  *
      35                 :            :  * This class is given a stream of equalities in calls to addRewrite(...).
      36                 :            :  * The goal is to show that a subset of these can be inferred from previously
      37                 :            :  * asserted equalities.  For example, a possible set of return values for
      38                 :            :  * add rewrite on successive calls is the following:
      39                 :            :  *
      40                 :            :  *   addRewrite( x, y ) ---> true
      41                 :            :  *   addRewrite( f( x ), f( y ) ) ---> false, since we already know x=y
      42                 :            :  *   addRewrite( x, z ) ---> true
      43                 :            :  *   addRewrite( x+y, x+z ) ---> false, since we already know y=x=z.
      44                 :            :  *
      45                 :            :  * This class can be used to filter out redundant candidate rewrite rules
      46                 :            :  * when using the option sygusRewSynth().
      47                 :            :  *
      48                 :            :  * Currently, this class infers that an equality is redundant using
      49                 :            :  * an instance of the equality engine that does congruence over all
      50                 :            :  * operators by mapping all operators to uninterpreted ones and doing
      51                 :            :  * congruence on APPLY_UF.
      52                 :            :  *
      53                 :            :  * TODO (#1591): Add more advanced technique, e.g. by theory rewriting
      54                 :            :  * to show when terms can already be inferred equal.
      55                 :            :  */
      56                 :            : class DynamicRewriter
      57                 :            : {
      58                 :            :   typedef context::CDList<Node> NodeList;
      59                 :            : 
      60                 :            :  public:
      61                 :            :   DynamicRewriter(Env& env, context::Context* c, const std::string& name);
      62                 :         39 :   ~DynamicRewriter() {}
      63                 :            :   /** inform this class that the equality a = b holds. */
      64                 :            :   void addRewrite(Node a, Node b);
      65                 :            :   /**
      66                 :            :    * Check whether this class knows that the equality a = b holds.
      67                 :            :    */
      68                 :            :   bool areEqual(Node a, Node b);
      69                 :            :   /**
      70                 :            :    * Convert node a to its internal representation, which replaces all
      71                 :            :    * interpreted operators in a by a unique uninterpreted symbol.
      72                 :            :    */
      73                 :            :   Node toInternal(Node a);
      74                 :            :   /**
      75                 :            :    * Convert internal node ai to its original representation. It is the case
      76                 :            :    * that toExternal(toInternal(a))=a. If ai is not a term returned by
      77                 :            :    * toInternal, this method returns null.
      78                 :            :    */
      79                 :            :   Node toExternal(Node ai);
      80                 :            : 
      81                 :            :  private:
      82                 :            :   /** index over argument types to function skolems
      83                 :            :    *
      84                 :            :    * The purpose of this trie is to associate a class of interpreted operator
      85                 :            :    * with uninterpreted symbols. It is necessary to introduce multiple
      86                 :            :    * uninterpreted symbols per interpreted operator since they may be
      87                 :            :    * polymorphic. For example, for array select, its associate trie may look
      88                 :            :    * like this:
      89                 :            :    *   d_children[array_type_1]
      90                 :            :    *     d_children[index_type_1] : k1
      91                 :            :    *     d_children[index_type_2] : k2
      92                 :            :    *   d_children[array_type_2]
      93                 :            :    *     d_children[index_type_1] : k3
      94                 :            :    */
      95                 :            :   class OpInternalSymTrie
      96                 :            :   {
      97                 :            :    public:
      98                 :            :     /**
      99                 :            :      * Get the uninterpreted function corresponding to the top-most symbol
     100                 :            :      * of the internal representation of term n. This will return a skolem
     101                 :            :      * of the same type as n.getOperator() if it has one, or of the same type
     102                 :            :      * as n itself otherwise.
     103                 :            :      */
     104                 :            :     Node getSymbol(Node n);
     105                 :            : 
     106                 :            :    private:
     107                 :            :     /** the symbol at this node in the trie */
     108                 :            :     Node d_sym;
     109                 :            :     /** the children of this node in the trie */
     110                 :            :     std::map<TypeNode, OpInternalSymTrie> d_children;
     111                 :            :   };
     112                 :            :   /** the internal operator symbol trie for this class */
     113                 :            :   std::map<Node, OpInternalSymTrie> d_ois_trie;
     114                 :            :   /** cache of the above function */
     115                 :            :   std::map<Node, Node> d_term_to_internal;
     116                 :            :   /** inverse of the above map */
     117                 :            :   std::map<Node, Node> d_internal_to_term;
     118                 :            :   /** stores congruence closure over terms given to this class. */
     119                 :            :   eq::EqualityEngine d_equalityEngine;
     120                 :            :   /** list of all equalities asserted to equality engine */
     121                 :            :   NodeList d_rewrites;
     122                 :            : };
     123                 :            : 
     124                 :            : }  // namespace quantifiers
     125                 :            : }  // namespace theory
     126                 :            : }  // namespace cvc5::internal
     127                 :            : 
     128                 :            : #endif /* CVC5__THEORY__QUANTIFIERS__DYNAMIC_REWRITER_H */